In robot applications where the robot is required to move between multiple work stations to perform operations on large stationary objects, such as an airplane wing, the provision of durable and reliable transporting systems capable of consistently and accurately positioning the robot at each successive work station has proven to be a challenging problem. Typically, some form of hardened boxway slide or tracking is utilized for guiding and transporting the robot. To achieve the desired accuracy and durability, prior art systems have proven to be very costly. For example, ball and roller systems and boxway systems require constant and thorough lubrication. Long travel distances, high speeds and heavy loads combine to create severe environmental problems, these problems being further compounded by the deleterious effect of dirt, paint, welding spatter and so forth which is often present and which tends to accelerate wear and increase friction in the driving system.
The accuracy of conventionally transported and driven robot systems generally depends upon the accuracy of the entire track installation. Long travel distances therefore require a very expensive foundation and installation procedure, and regular realignment is required even with the best of foundations, usually with a laser.
The provision of means for driving slideways over long distances also creates problems. Cylinders or ball screws are not practical, and the usual solution is the use of a rack and pinion. If the robot-supporting saddle and its load are heavy, a heavy rack is required. Such a rack has to be aligned to the base of the slideway with virtually the same degree of accuracy as is required for the ways. For high transport speeds, a coarse pitch is generally required, which in turn necessitates heavy bearings on the pinion to prevent the pinion from climbing out of the rack. If the pinion axle is vertical, then saddle space is consumed by the motor unit, requiring a longer saddle and greater wasted travel at one end of the ways. The rack also must be protected from dirt, and often consume valuable space between the way rails.
Heretofore, the use of wheels and tires was generally not practical, because of the required accuracy of the tracking and because the carriage would rock on its tires when the robot arm was extended laterally across the tracks when the robot was in operation, introducing unreliable positioning of the robot. Such overhung loads on the robot arms also presented a safety problem.
Accordingly, it is the principal object of the present invention to provide an improved transporter system for robots which provides consistent accuracy of robot location at multiple work stations without the requirement of costly foundation systems and periodic realignment, and which is capable of rapid travel without lubrication and wear problems.